SOUTH BRISTOL — A homeowners group fighting a planned multimillion-dollar residential development at Bristol Harbour over environmental concerns on Thursday filed an appeal in state Supreme Court.

“The matter is urgent,” said attorney Frank Aloi, who represents Bristol Homeowners Environmental Preservation Associates LLC. After Ontario County Surrogate Court Judge Frederick Reed dismissed the case this past fall, Aloi said, he began working on the appeal on the group’s behalf. He is advocating the case be heard as soon as possible, he added.

“If you crash bang with construction, even routine construction, nothing special, that shale base is liable to start disintegrating in the rains of spring and autumn, and bring mudslides,” said Aloi, who is also an owner of a condo on Cliffside Drive. “And when it goes downhill, it goes into Bristol Harbour condos.”

At issue is a planned 24-unit condominium development on vacant, wooded land in Bristol Harbour above Cliffside Drive. Several condominium owners adjacent the land took their concerns over shale erosion, flooding, lake pollution and loss of green space to court — naming the town of South Bristol and its Planning Board, which approved the plan; Bristol Harbour owners South Bristol Resorts LLC/Bristol Harbour Development LLC; and project developer, Chrisanntha Construction, Iversen Construction and Christopher Iversen.

Bristol Homeowners also challenged the town’s approval process, which began with a first approval in 2006 and most recently with an approval in October 2012, after the project was altered from a 24-lot subdivision to a one-lot subdivision for a condo development with 24 units.

“There have never been public hearings concerning both the lapsed site plan approval . . . and compliance with the new Steep Slope Law,” stated a Memorandum Of Concern from the group by attorneys Frank Aloi and Robert Lunn.

“Surface water drainage, and erosion of steep slopes has been a concern for quite some time in the immediate environs of the SBR/Iversen project,” the memorandum also stated, adding the problem of flooded yards and basements remains unresolved. “The unavoidable truth is that water flows downhill, and not only the Lakewood Trail homes but also the Bristol Harbour Condominiums are directly in the path of surface water runoff, that we do not believe can be contained, despite all good intentions.”

Another argument outlined in the document: The plan’s removal of trees and ground cover from the site before construction. “We frankly cannot fathom how that aspect of the development plan squares with the Town of South Bristol, statement of intent for subdividing property,” stated the attorneys, citing town code that calls for preservation of natural and historic features.

South Bristol Town Supervisor Barbara Welch, a former town board member who became supervisor Jan. 1, said she was educating herself about the case and declined to comment.

Alan Knauf is the attorney representing South Bristol Resorts/Bristol Harbour Development and the developer. He said the homeowners’ case lacks merit for a number of reasons and he expects the outcome of the case to remain the same after the appeal is decided.

“Everything was done too late . . . decisions were made over course of years and there was no appeal to the Zoning Board,” he said. Neither was the case brought within the time limit to allow for an Article 78 proceeding, said Knauf, referring to a proceeding used to appeal the decision of a state or local agency to the New York courts.

Developer Chris Iversen also expressed confidence. “The case has been decided,” he said Friday. He added that the homeowners case is based on fear and “false information.” “They have not read that their fears were addressed in the planning stages,” he said. For example, erosion issues were addressed before the site plan was granted in 2009, Iversen said. “Engineering was an extensive process” that involved working for more than a year with the state Department of Environmental Conservation “to come up with a plan to mitigate concerns,” Iversen said. “We have put a lot of safeguards in place.”

Iversen added that a much denser plan was pitched before this one, leaving him to wonder why this plan has raised a ruckus.

Iversen said he hopes the project can begin this year. He and his team are assessing the market, he said, and the approval from the DEC needs to be renewed.

As for the environmental issues, watershed consultant Steve Lewandowski said “the homeowners should have spoken out years ago.” He added that he and other citizens voiced concerns when the project was first proposed. “We were ignored,” he said. Describing the development site as “steep and on a long, narrow piece of property that includes a gully at one end,” Lewandowski said, “It will not be easy to control.”

Aloi said the case will be heard the state Appellate Division, 4th Department in Rochester. The defendants will first receive an order from the Appellate Division setting the date when their answering briefs must be filed, which will be at least 30 days out. Then, oral arguments will be scheduled.